What is the Difference Between Synthetic Progestins & Progesterone?

Synthetic progestins and progesterone are not the same

by Christiane Northrup, M.D.


It’s 2002 all over again, and women are being warned against taking hormone replacement because of its link to breast cancer. Why is history repeating itself? Because we haven’t learned an important lesson. Synthetic progestins are not the same as progesterone, and reporting on them as if they confer the same risks and benefits is absurd.

Risks of Hormone Therapy

A study in the New England Journal of Medicine dated February 5, 2009, concluded that hormone therapy doubles the risk of breast cancer. Specifically, women past menopause who take both estrogen and progestin (such as in the form of Prempro) for five years or more have twice the risk of developing breast cancer. When these same women stopped their combination hormone formula, the number of breast cancer incidents dropped by about 28 percent within the first year.

This study is a follow-up to the landmark Women’s Health Initiative that studied more than 15,000 women between the ages of 50 and 79 who were taking HRT. In 2002, the study was stopped when researchers concluded that Prempro caused higher incidents of heart problems and breast cancer. Interestingly, the number of breast cancer cases dropped significantly since 2003. Dr. Rowan Chlebowski, a medical oncologist at Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, wanted to know why. So he assembled a team of researchers to determine if it was due to women halting their HRT or to more vigilant mammography practices.

It’s related to HRT use; getting regular mammograms didn’t affect the numbers at all. But it’s not related to all hormone therapy! The women who took only estrogen (usually in the form of Premarin) without the progestin were no more likely to develop breast cancer than women who took no hormones at all. (Progesterone lowers the risk of uterine cancer. Women without a uterus aren’t typically given a progestin.) This means the synthetic progestin is the likely culprit.

Flashback to 2002. Women around the world stopped HRT cold turkey, causing many to feel unhealthy. Why? Because many healthcare providers and researchers didn’t know or appreciate the difference between a synthetic progestin and progesterone, which is a bioidentical hormone. (For more information on bioidentical hormones, read “The ABCs of HRT“) 

Benefits of Progesterone

Progesterone matches a woman’s body exactly and has been shown to ease mood, sleep, and cycle-related issues. Progesterone supplementation has another unique advantage—it can be converted to other hormones, such as testosterone and DHEA, if needed. Synthetic progestin is an altogether different substance known to actually exacerbate perimenopausal and post-menopausal symptoms—in addition to increasing your risk of breast cancer, heart disease, and stroke.

Related Reading: 3 Drugs I Would Not Take

It’s hard to believe that seven years have passed and yet the difference between synthetic progestins and progesterone is not widely understood. Dr. Northrup has been doing her best to educate women across the U.S. and the world and has recently appeared on TV, radio, and webcasts to share her knowledge. She encourages all women to learn about all the options for hormone therapy available today, particularly those involving bioidentical hormones. Dr. Northrup also hopes that all women will look with a critical eye at mainstream news about HRT, especially the news that’s sensationalized. As is the case with the study described above, there’s more to the story than meets the eye.

Learn More — Additional Resources

Last Updated: February 17, 2009

Christiane Northrup, M.D.

Christiane Northrup, M.D., is a visionary pioneer and a leading authority in the field of women’s health and wellness. Recognizing the unity of body, mind, and spirit, she empowers women to trust their inner wisdom, their connection with Source, and their ability to truly flourish.


Add comment
  1. Juliane
    8 months ago

    I am post menopausal. Is it ok to take USP pharm grade bioidentical Estrogen transdermally along with USP Bio identical Progesteron transdermally? This would be my preference however I also read somewhere (and hoping this is wrong) that one must take the Progesterone systemically, either orally or as an IUI, to protect against uterine wall thickening. Is this not true and I can stick w/ my current transdermal protocol.

  2. David Hawkins
    8 years ago

    I won’t get into detail, but my doctor has said hormone replacement therapy might be good for my condition. We’ve gone over the risks, but we feel the potential benefits really outweigh them. For me, I’m just trying to stay as informed about all kinds of hormonal therapy that there are. Thanks for posting these awesome details on the process!

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